Vaporized hydrogen peroxide (VHP®) is used for decontamination of enclosed and sealed areas. It is capable of destroying all forms of microbial life, including bacteria, bacterial spores, fungi, fungal spores, and viruses. It is commonly produced from a solution of liquid H2O2 and water, by means of generators specifically designed for the purpose. Aqueous hydrogen peroxide may be supplied as a 35% stabilized solution, for example Vaprox® supplied by Steris Corporation.
For producing hydrogen peroxide vapor, several methods have been developed and suggested. In WO2007003313 is disclosed the impingement of a spray of hydrogen peroxide solution on a heat transfer surface to generate gaseous agent. This has been said to cause buildup of impurities on the heat transfer surface. According to U.S. Pat. No. 5,258,162, a spray of hydrogen peroxide solution may instead be introduced in a heated carrier gas stream which conveys the energy required for atomization. In EP 2 286 846 is disclosed how the atomization may be effected using ultrasound. In WO2011076400, a flash evaporator is disclosed having a series of wells in a heating block, into which wells hydrogen peroxide solution can be individually fed. A gas stream in a flow channel above the wells carries the total vaporized material from the series of wells to the point of use. In U.S. Pat. No. 5,997,827 is disclosed a device having a porous tube section which hydrogen peroxide solution penetrates, vaporizing into a heated air stream flowing to a feed tube. The vaporizing section and the feed tube are steam heated.
In this context, “steam” refers to water in gaseous or condensing form. “Vacuum” refers to a pressure below atmospheric.
Certain products, e.g. products containing heat-sensitive biological material in aqueous solution or in dry form, require sterilization at relatively moderate temperatures due to the thermal sensitivity of the materials involved. Proteins, steroids and vaccine components are examples. In such cases, the use of vacuum, steam and hydrogen peroxide vapor is often an adequate solution. By means of pressure control, the temperature of the steam and the hydrogen peroxide vapor can be adjusted to a desired level. A lower pressure corresponds to a lower temperature in the steam and the hydrogen peroxide vapor.
An apparatus for sterilization using a closed space in which goods are treated with hydrogen peroxide vapor requires, in addition to a source of hydrogen peroxide, a source of steam for heating the enclosure to which the load is confined to the maximum temperature allowed.